Opto-mechanical devices with sharp-edge lenses

ABSTRACT

An opto-mechanical device, such as a lens cell, includes a housing having an axially extending chamber and an intermediate internal spacer that positions a sharp-edged lens in the chamber. The sharp-edged lens has first and second optical surfaces that intersect in a circumferential sharp edge. The housing positions an image sensor proximal to the sharp-edged lens for processing light therefrom.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 61/646,769 for Opto-Mechanical Devices with Sharp-EdgedLenses filed May 14, 2012 and assigned to the same assignee as thisinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to opto-mechanical devices forproducing images to be displayed and more specifically toopto-mechanical devices for use in procedures requiring miniaturizedimaging devices.

2. Description of Related Art

In recent years endoscopic and other like imaging systems have beendeveloped to display an image on a video monitor. These imaging systemstypically include opto-mechanical devices with housings for supportingoptical devices such as objectives of one or more lenses. An objectiveforms an image for being conveyed to a remote video processor. In someapplications, an image sensor proximate the objective interfaces withthe objective and converts the incoming light from the objective intodigital signals that are coupled to a video processor. Otherapplications define an interface for one end of a coherent fiber bundleand an objective; the other end of the bundle terminates with a remoteconnection to the video processor. In either embodiment glass objectivesare preferred for good image quality.

Customers for such devices, particularly in the medical field, alsoexpress a desire for imaging systems with minimal cross-sections,particularly systems that can be manufactured at low cost and in highvolumes for single-use, disposable instrumentation. Recently imagingsensors have become available with cross-sections of less than 2 mm. andwith pixel densities that provide good image resolution. However, priorart optical devices have not been available for interfacing with suchimage sensors in commercially acceptable production quantities andcosts.

As known, the production of a larger, conventional lens involvesgrinding and polishing end surfaces of an optical glass blank to formtwo polished spherical optical surfaces spaced along an axis. Each lensthen undergoes edge grinding to reduce the lens diameter to a specifiedvalue and to align the optical and mechanical axes. U.S. Pat. No.7,715,105 (2010) to Forkey et al. for an Acylindrical Optical Devicediscloses an alternative by which small diameter lenses are manufacturedfrom over-sized lens elements and other optical elements formed intolens systems. Edges are sawn into each lens system to reduce its overallsize. Sawing can be applied to integral lens elements or lens arrays. Asan alternative, lenses also can be molded from glass or plastic.Photolithographic techniques constitute another alternative that can beused to fabricate lenses on a wafer, such as included in an imagesensor.

Prior art molding processes become difficult to implement for theproduction of small lenses with diameters less than 2 mm. It isdifficult to obtain acceptable resolution with plastic lenses of thissize. Edge grinding, such as used with manufacture of standard lenses,must be undertaken with tighter controls for increased accuracy. Edgegrinding is also time-consuming and therefore increases manufacturingcosts. The above mentioned sawing process may not be appropriate fornewer applications, particularly those which require high-volume, lowcost production. Lithographic processes can be applied only to a limitednumber of materials and have limited radii of curvature. Consequentlythey are unlikely to provide a lens with a high index of refractionand/or short radius of curvature as is required for obtaining a largefield of view with small lenses.

What is needed is an opto-mechanical assembly constructed with adiameter of in the order of 2 mm or less that can interface with a smallimage sensor or coherent fiber bundle wherein the opto-mechanicalassembly can be provided in sufficiently large volumes and atsufficiently low costs such that instruments incorporating suchassemblies can be made as disposable instruments or components thereof.

SUMMARY

Therefore it is an object of this invention to provide anopto-mechanical assembly to be constructed with a small glass lens forbeing interfaced with components for conveying an image to a remoteimage processor.

Another object of this invention is to provide an opto-mechanicalassembly with a small glass lens and an image sensor at reasonableproduction costs at high volumes.

Still another object of this invention is to provide an opto-mechanicalassembly with a small glass lens and an interface for a coherent fiberbundle for conveying an image to a remote image processor at reasonableproduction costs and high-volumes.

In accordance with one aspect of this invention an opto-mechanicalassembly comprises a lens having first and second polished surfaces thatintersect in a sharp edge at the periphery thereof. A support carriesthe lens.

In accordance with another aspect of this invention, an opto-mechanicalassembly comprises a lens having first and second polished surfaces thatintersect in a sharp edge at the periphery thereof. A support in form ofa housing carries the lens. A processor supported by the housingreceives light from the lens and the housing includes a structure thatpositions the lens and the processor in an operative relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended claims particularly point out and distinctly claim thesubject matter of this invention. The various objects, advantages andnovel features of this invention will be more fully apparent from areading of the following detailed description in conjunction with theaccompanying drawings in which like reference numerals refer to likeparts, and in which:

FIG. 1 is a perspective view of a portion of an endoscope thereof takenfrom the distal end with an opto-mechanical assembly in the form of alens cell that can incorporate this invention;

FIG. 2 is a cross-section of a prior art opto-mechanical device;

FIG. 3 is a cross-section of one embodiment of an opto-mechanical devicethat incorporates a sharp-edged plano-convex lens of this invention;

FIG. 4 is a plan view of a sharp-edged bi-convex lens that could beincorporated in other opto-mechanical devices;

FIG. 5 is a plan view of a sharp-edged concave-convex lens that could beincorporated is still other opto-mechanical devices; and

FIG. 6 is a cross-section view of another embodiment of anopto-mechanical device that utilizes a convex-plano lens carried by asupport in the form of a housing.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 discloses a portion of an endoscope 10 viewed from a distal end11 that depicts an illumination channel 12 and an imaging lumen 13within a flexible sheath 14. A portion of the sheath 14 is cut away todisplay an opto-mechanical assembly in the form of a lens cell 20 thatincludes imaging optics and an image sensor that connects throughconductors 21 and 22 to an electronic imaging system (not shown) thatprocesses and displays the image formed by an objective in the lens cell20. Such electronic imaging systems are well known in the art.

FIG. 2 discloses a lens cell 30 including a prior art opto-mechanicaldevice. A housing 31, which may have a cylindrical or othercross-section, includes an integral annular positioning band 32 that isintermediate distal and proximal portions 33 and 34. An image sensor 35with its conductors 36 and 37 abuts a proximal shoulder formed by theannular band 32. A conventional plano-convex lens 40 has its planarsurface 41 abutting a distal shoulder on the annular band 32. Adhesivematerial 38 in peripheral gaps between the housing 31 and each of theimage sensor 35 and lens 40 provides axial component stability. Thedistance between the lens 40 and the imaging sensor 35 is based upon thefocal length of the lens 40 and the particular application for theinstrument containing the opto-mechanical device 30. Methods fordetermining such spacing are well known to those of ordinary skill inthe art.

As previously indicated, opto-mechanical devices, such as the device 30,are difficult to manufacture as the diameters of the lens and housingreduce into the range of 2 mm or less. FIG. 3 depicts a cross-section ofone embodiment of the lens cell 20 in FIG. 1 that incorporates thisinvention. This lens cell 20 includes a lens support in the form of ahousing 41 with an annular positioning band 42 that is intermediatedistal and proximal portions 43 and 44. In this embodiment acommercially available small image sensor 45 is positioned against aproximal shoulder of the annular positioning band 42. Conductors 46 and47 provide an interface between the image sensor 45 and remote imageprocessing equipment and correspond to the conductors 21 and 22 in FIG.1.

Still referring to FIG. 3, an objective lens 50 is positioned againstthe distal shoulder of the annular band 42 and held in place withadhesive material 51 about the periphery of the lens 50. The objectivelens 50 in this particular embodiment is a plano-convex lens with aconvex polished surface 52 facing distally and a planar polished surface53 facing proximally toward the image processor 45.

The objective lens 50 is a sharp-edged lens. Specifically, it is a lensformed by two optical surfaces 52 and 53 that intersect at an anglethereby forming a sharp edge 54 about the periphery of the lens whichhas not been subjected to any edge grinding. Thus, the manufacturing ofthe sharp-edged lens 50 of FIG. 3 avoids the expense and time for edgegrinding that would otherwise be required to reduce the diameter of alens into the range of 2 mm or less. Moreover a sharp-edged lens, suchas the objective lens 50, is self centering. That is, during manufacturethe intersection of the optical surfaces generates an outside diameterthat is automatically aligned with the center of the optical surfaces.It will also be apparent that only a minimal effort is required tosecure the lens 50 into the housing 41, as by the simple application ofadhesive material 51.

Sharp-edged lenses have not been widely adopted in optics manufacturing.This is, in part, due to the potential that small shocks can cause thesharp edge of a larger lens to break. However, small sharp-edged lensesto which this invention is directed have a smaller mass. Two otherfactors are involved. First, circumference is proportional to lensdiameter. Force on a lens due to shock is proportional to the mass ofthe lens which, in turn, is approximately proportional to the diameter,d, of the lens cubed (i.e., d³). Force per unit length of a sharp edgeat the lens periphery is proportional to the diameter squared (i.e.,d²). Consequently as the diameter of a lens decreases into the range atwhich this invention is directed, the force per unit length at the sharpedge decreases dramatically and a sharp-edge lens having a diameter in arange of less than 2 mm can withstand normally encountered adverseeffects of shocks and other forces.

Other lens shapes can be used with the same benefits for otherapplications. FIG. 4, for example, depicts a view of a biconvex lens 60that has spherical optical surfaces 61 and 62 that intersect along asharp edge 63. FIG. 5 depicts a concave-convex lens 64 with a concavepolished surface 65 and a convex polished surface 66 that form a sharpedge 67.

FIG. 6 depicts an opto-mechanical device 70 with a support 71 forcarrying a convex-plano lens 72 on an axis 73 in accordance with thisinvention. A knife edge 76 is formed about the periphery of the lens 72at the intersection of the polished planar surface 74 and the adjacentsurface of the spherical portion 75 of the lens 72. The device 70, suchas shown in FIG. 6, can include a tubular housing 77 with an internalcircumferentially extended annular shoulder 80. Adhesive 81 can beapplied to the radial shoulder surface against which the peripheralportion of the planar surface is pressed to lock the lens 72 in place.Alternatively or in addition, adhesive 82 could be applied to the lens72 and housing 77 at a gap 83 proximate a point of contact between lens72 and the housing 77.

As now will be apparent, an opto-mechanical assembly or lens cell inaccordance with this invention includes a sharp-edged lens and interfacefor conveying the image to a remote image processing system. The use ofsharp-edged lenses enables the manufacture of such lens cells in highvolumes and at low cost. This could be particularly important indesigning a lens cell, such as the lens cell 20 in FIGS. 1 and 3, at asufficiently low cost to justify its inclusion in a disposableinstrument thereby significantly reducing cleaning costs that areotherwise required in the medical and other fields. Such an assembly canbe constructed with an interface to an image sensor included with theassembly or to a coherent fiber bundle as will be apparent to thoseskilled in the art.

This invention has been disclosed in terms of certain embodiments. Manymodifications can be made to the disclosed apparatus without departingfrom the invention. For example, this application shows severalembodiments of sharp-edged lenses useful in accordance with thisinvention. Embodiments with other configurations could be substituted.Specific cylindrical housing configurations have been disclosed;alternative housing configurations could be substituted. Therefore, itis the intent of the appended claims to cover all such variations andmodifications as come within the true spirit and scope of thisinvention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. An opto-mechanical assembly comprising: A) alens having a diameter of less than about 2.0 mm and wherein such lensfurther has first and second polished surfaces that intersect in a sharpedge at the periphery thereof, and B) a support that carries said lens.2. The opto-mechanical assembly as recited in claim 1 wherein said firstand second polished surfaces define a lens taken from the groupconsisting of plano-convex, concave-convex and biconvex lenses.
 3. Theopto-mechanical assembly of claim 1 wherein said support includes anintegral annual positioning band for positioning said lens in saidsupport.
 4. The opto-mechanical assembly of claim 3 additionallyincluding adhesive about the periphery of said lens thereby to securesaid lens in said support.
 5. An opto-mechanical assembly comprising: A)a lens having a diameter of less than about 2.0 mm and wherein such lensfurther has first and second polished surfaces that intersect in a sharpedge at the periphery thereof, B) a housing that caries said lens, C)processing means mounted to said housing for receiving light from saidlens, and D) means for positioning said lens and said processing meanswith respect to said housing in an operative relationship.
 6. Theopto-mechanical assembly as recited in claim 5 wherein said first andsecond polished surfaces define a lens taken from the group consistingof plano-convex, concave-convex, and biconvex lenses.
 7. Theopto-mechanical assembly as recited in claim 5 wherein said positioningmeans includes an integral annular positioning band in said housing thatdefines a shoulder for positioning said lens within said housing.
 8. Theopto-mechanical assembly as recited in claim 7 additionally includingadhesive about the periphery of said lens thereby to secure said lens insaid housing against a first shoulder.
 9. The opto-mechanical assemblyas recited in claim 7 wherein said first and second polished surfacesdefine a lens taken from the group consisting or plano-convex,concave-convex, and biconvex lenses.
 10. The opto-mechanical assembly asrecited in claim 5 wherein said positioning means includes an integralannular positioning band in said housing with first and second shouldersfor positioning said lens and said processing means in a spacedrelationship within said housing.
 11. The opto-mechanical assembly asrecited in claim 10 additionally including adhesive about theperipheries of said lens and said processing means to secure said lensand said processing means in said housing against first and secondshoulders, respectively.
 12. The opto-mechanical assembly as recited inclaim 10 wherein said first and second polished surfaces define a lenstaken from the group consisting of plano-convex, concave-convex, andbiconvex lenses.